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There are several different kinds of bone cancer — including osteosarcoma , Ewing’s sarcoma, and chondrosarcoma — that are known as primary bone cancers. Cancer that spreads to bone after originating in other organs is not technically bone cancer, but rather metastatic bone cancer. For instance, cancer that begins in the prostate and later spreads to bone is referred to as prostate cancer with bone metastases.

Risk Factors for Bone Cancer

While researchers don't know the exact cause of bone cancer, many risk factors have been identified. Risk factors for primary bone cancer include:

noncancercous bone diseases

genetics

high-dose radiation treatment for other cancers

cancer in another organ in the body that may spread to bones

Bone Cancer Risk: Noncancerous Bone Diseases

A number of health conditions that attack a person's bones can create an increased risk of bone cancer. These disorders include:

Paget's disease: This condition can affect one or more bones, causing abnormal bone tissue to develop. The abnormal tissue makes bones heavy, thick, and brittle. Bones with Paget's disease tend to be weaker and more likely to break but, overall, the disease usually is not life threatening. Osteosarcoma develops in about 1 percent of people suffering from Paget's disease, but usually not until the Paget’s disease has spread to several bones.

Benign bone tumors: The formation of noncancerous bone tumors in the body increases a person's risk of bone cancer. These benign tumors include chondromas, which can grow in cartilage, and osteochondromas, which can form in bone and cartilage.

Multiple exostoses: This inherited condition causes many bumps to form on a person's bones. These bumps, benign tumors consisting of cartilage, can make bones deformed or weak. Multiple exostoses create an increased risk of chondrosarcoma, a bone cancer that begins in cartilage.

Ollier's disease: Also known as enchondromatosis, this disease causes multiple benign tumors to form in the body's cartilage. People with Ollier's disease have a higher risk of chondrosarcoma.

Maffucci's syndrome: This condition causes benign bone tumors and abnormally shaped bones. Approximately 20 percent to 40 percent of people who develop this disease may also develop chondrosarcoma.

Bone Cancer Risk: Genetic Factors

Diseases that are not related to the bones but are inherited through a genetic factor have also been shown to increase the risk of bone cancer. These diseases include:

Hereditary retinoblastoma: This rare eye cancer affects children and is caused by a genetic mutation. Kids with this mutation have an increased risk of bone cancer, especially if radiation therapy is used to treat the retinoblastoma.

Li-Fraumeni syndrome: This genetic mutation increases a person's risk of developing a number of cancers, including the bone cancer osteosarcoma, as well as cancers of the breast and brain.

Rothmund-Thompson syndrome: Kids with this genetic syndrome suffer from stunted growth and skeletal problems. They are more likely to develop osteosarcoma.

Bone Cancer Risk: Radiation

Bone cancer can be caused by exposure to radiation. Normal X-rays of bones are considered relatively harmless, but high-dose radiation therapy targeting a part of the body that includes bones increases the risk of bone cancer developing in the area that was treated. It is a small risk, however. Only one patient in every several hundred treated with radiation therapy will end up developing bone cancer. However, the risk is greater for children receiving radiation treatment for cancer than for adults receiving similar treatment.

Bone Cancer Risk: Metastatic Disease

Bones are a common target for cancer cells that break off from a primary tumor elsewhere in the body. These cells enter the bloodstream and look for other places to invade. Cancer that has spread into the skeleton from another organ most often occurs in bones near the center of the body, as opposed to primary bone cancers, which tend to start in the long bones of the limbs. The spine is the most common place for metastatic bone cancer to invade, followed by the pelvis, upper leg bone, upper arm bone, ribs, and skull.